Commercial Mortgage Residual Interests (Schedule Of Amounts Recognized As Unrealized Gains And/Or Losses Recorded As Other Comprehensive Income And Other Than Temporary Valuation Impairments Recorded In Earnings) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Commercial Mortgage Residual Interests [Abstract]
Unrealized gains	$ 0	$ 1,272	$ 0
Unrealized losses	246	0	1,744
Other than temporary valuation impairment	$ 1,024	$ 3,995	$ 498